Q&A: Stained Vinyl Floors

Stained Vinyl Floors

Q.I’ve built a number
of homes with staple-up radiant heat tubing under vinyl
flooring in the kitchens and baths. Recently a client
complained of staining in his vinyl floors. In the
bathroom, long dark streaks are bleeding up through the
vinyl, and in the kitchen, small dark circles about the
size of a quarter are forming. The staining is getting
worse with time. The vinyl manufacturers claim that
it’s a problem with the radiant heating and
the subflooring. I lifted the vinyl and discovered that
wherever discoloration occurred, there was a bleeding
knot in the plywood below. I have never experienced
this problem before. Any ideas?

A.Paul Fisette,
director of the Building Materials and Wood
Technology program at the University of
Massachusetts in Amherst, responds: The
problem you describe is not unique, though
it’s fairly uncommon. What is happening,
as you guessed, is that volatile compounds are
being released from the plywood and are reacting
with the vinyl to cause the staining. White and
light-colored vinyls are usually the only ones that
experience this discoloration. The problem has
three aspects: the radiant heating, the
underlayment, and the flooring itself.

The "long dark streaks" sound like they could be
associated with the " striping" effect that happens
with radiant floors when the tubes are spaced too
far apart and the fluid temperature is too high
(see "Hardwood Flooring Over Radiant Heat," 9/98,
for more on striping). With staple-up systems in
particular, the fluid temperature is typically
higher, to compensate for having to drive the heat
through the plywood subfloor. Since the tubing has
no conductive medium to disperse the heat
— like the concrete in radiant slabs
— the striping effect may be more
pronounced with staple-up systems. It’s
quite possible that these "hot spots" are causing a
reaction between the vinyl flooring and volatile
compounds in the plywood or chemicals in the vinyl
adhesive.

You might check with your hvac contractor to see
if the fluid temperature in the tubing can be
reduced. On future jobs, plan to space the tubing
closer so the fluid temperatures can be lower.

The second aspect of the problem is the
underlayment. According to the APA (American
Plywood Association), rated underlayments should
not experience problems from the low temperatures
associated with radiant heat. By this they mean
that no structural damage will ensue, but they make
no guarantee that volatile compounds won’t
be released. A frustrating part of this issue is
that manufacturers of underlayment and vinyl
flooring have not worked together to craft a
solution, and seem more inclined to point fingers
at each other. APA holds vinyl as the villain: It
claims that plasticizers and other chemicals found
in moderate- to low-cost vinyl react with pitch and
volatile compounds naturally found in the wood
panels, and that exposure to heat and sunlight
speeds the darkening process along. APA’s
recommendation is for builders to use better
quality vinyl.

On the other hand, makers of resilient flooring,
the third piece of this puzzle, claim there is
nothing wrong with the vinyl but rather that the
underlayment and adhesives used to glue subflooring
to the floor joists contaminate the vinyl. Like the
APA, vinyl manufacturers typically warrant the use
of their products with radiant heat, but limit the
temperatures involved. Armstrong, for instance,
limits floor surface temperature to
85°F.

As for solving your problem, representatives of
the vinyl industry recommend that you strip the
discolored vinyl, remove the offending
underlayment, then replace it with an underlayment
whose manufacturer will guarantee it won’t
stain the finish flooring. (Good luck with that
one!)

You might want to consider using lauan plywood
as an underlayment, since it contains far fewer
volatile compounds. However, be advised that using
lauan may void the warranty on some flooring
products, because underlayment-grade plywood is
virtually the only material allowed in warranty
specs.

Beyond these suggestions, your options are
limited. If you’re using a
perimeter-attached vinyl and you can clearly
identify the locations of the spotting, peel the
flooring back and tape (use masking tape) pieces of
aluminum foil over the offending knots to block the
diffusion of volatiles and pitch. If you are using
a fully-adhered sheet vinyl, use an underlayment
that is guaranteed not to react with vinyl
— if you can find one. You might also
encourage your clients to choose darker vinyl
colors.

One encouraging note for the future: Problems
like yours are reportedly becoming a thing of the
past as vinyl flooring manufacturers, aware of the
problem, develop products that resist reactive
staining. I would always choose a major
manufacturer and a higher-quality product.